Field
The present disclosure relates generally to memories, and more particularly, a memory operating a memory cell screen for BTI effect.
Background
Modern electronic devices (such as cell phones, smart watches, etc.) rely heavily on electronic circuits built from field effect transistors (FETs). Such FETs may include p-channel transistors (e.g., p-type metal-oxide-semiconductor or PMOS transistors) and n-channel transistors (e.g., n-type metal-oxide-semiconductor or NMOS transistors).
The electronic circuits built from these p-channel transistors and n-channel transistors are susceptible to the negative-bias temperature instability (NBTI or more generally, BTI) effect. BTI causes the threshold voltages (VTH) of the p-channel transistors and n-channel transistors to shift over time. For example, a VTH of a p-channel transistor subject to the BTI effect may rise up to 50 mV over time. A memory built from these devices may experience random fails as the VTH of the p-channel transistors shifts and rises.
Accordingly, there is a need for a stress mode of the memory to screen out weaker memory cells that are particularly susceptible to the BTI effect.